Add missing environment variables for prometheus container

Patch [1] broke the backward compatibility for the previous
version of the Prometheus container, see the bug below.

[1] https://gerrit.mcp.mirantis.net/#/c/13742/

Change-Id: Ie670f2bee7d0303896078dd0a365ff85fb853071
Closes-Bug: PROD-17030
1 file changed